Cabinet Office minister Francis Maude has denied reports of a rift with Work and Pensions Secretary Iain Duncan Smith over the troubled universal credit (UC) project.

Mr Maude admitted the initial implementation of the flagship scheme had been "pretty lamentable" - but insisted they were "working closely together" to fix the problems.

Leaked documents have revealed that the Cabinet Office accelerated the withdrawal of elite IT experts from the flagship scheme.

According to the Guardian, senior civil servants had been warned of delays and increased costs because of the Government Digital Service (GDS) pull-out.

One Whitehall official was quoted in the documents complaining that "friction between DWP (the Department for Work and Pensions) and Cabinet Office" had made things "more difficult than necessary".

It is understood the meeting took place before Mr Duncan Smith set out the next stages of the scheme in December, admitting that around 700,000 disabled claimants of Employment and Support Allowance will not be transferred on to UC by the target date of 2017.

The DWP insisted that "events have very much moved on" since the meeting took place.

A DWP spokeswoman said: "We set out plans last month for the future roll-out of Universal Credit and they have not changed. Our primary concern remains ensuring that this vital reform is delivered in a safe and secure way.

"We have been very clear that DWP would take over development of the new digital service following the initial GDS work.

"Our current plans will see all new benefit claimants claiming Universal Credit by 2016, with most existing benefit claimants moving on to Universal Credit during 2016 and 2017."

A separate document leaked to the Guardian made clear that the rapid withdrawal by the Cabinet Office experts was one of the most serious problems facing the project, which will replace a range of benefits with a single, simplified payment.

The risk assessment warned the DWP might not be "able to obtain the skills required to replace GDS within the current market at affordable cost".

Speaking at a briefing for journalists, Mr Maude said UC was an "excellent policy" and insisted the timing of the transition back to the DWP team had been consensual.

"The expectation always is that at some point the in-house team take over," he said. "The transition was very clearly agreed between the Cabinet Office and DWP."

He said the Cabinet Office had put a "lot of resource" into helping fix the problems with the universal credit project.

But he defended Mr Duncan Smith's handling of the situation, saying he had acted to stop more money being wasted.

"I think he did take responsibility, in that he asked for an inquiry, a review of what was going wrong," he said.

"If he had continued to believe what he was being told then actually it would have blundered on wasting even more money."

Mr Maude denied that he and Mr Duncan Smith had fallen out over UC.

"No, we haven't at all. We work very closely together," he said.

Shadow work and pensions secretary Rachel Reeves said: "Now we learn that Iain Duncan Smith's officials are warning of further delays, more wasted taxpayers' money and bickering between ministers.

"While families are facing a cost-of-living crisis, it's completely unacceptable that millions have been wasted because of failures by David Cameron and Iain Duncan Smith to get a grip of their flagship Universal Credit scheme."

Last month Whitehall's spending watchdog said the DWP had failed to achieve ''value for money'' in the development of UC, and needed to adopt ''realistic expectations'' on the timetable for its delivery.

The National Audit Office warning came after Mr Duncan Smith admitted that more than £40 million spent on IT for the project had been written off in 2012/13, with a further £91 million of software code expected to be written down in value to nil over the next five years.